Identification of a conserved linear epitope on the VP1 protein of serotype O foot-and-mouth disease virus by neutralising monoclonal antibody 8E8

Foot-and-mouth disease virus (FMDV) serotype O remains an important threat to animal husbandry worldwide, and the variability of the virus presents a major problem for FMDV vaccine design. High-affinity neutralising antibodies against a conserved epitope could provide protective immunity against diverse subtypes of FMDV serotype O and protect against future pandemics. We generated a novel monoclonal antibody (MAb) 8E8 that potently neutralised infection of FMDV O/YS/CHA/05 both in vitro and in vivo. Screening of a phage-displayed random 12-peptide library revealed that MAb 8E8 bound to phages displaying a consensus motif GDLNVRT, which is highly homologous to (146)GDLQVLT(152) of the FMDV VP1 protein. Given that MAb 8E8 showed reactivity with the (146)GDLQVLT(152) motif, we proposed that this motif represented a linear B-cell epitope of the VP1 protein. Western blot analysis revealed that the epitope peptide could be recognised by the positive sera from serotype O FMDV-infected pigs. The (147)DLQVLT(152) motif was the minimal requirement for reactivity as demonstrated by reactivity of MAb 8E8 with several truncated peptides derived from the motif. For further mapping, a set of different extended motifs derived from the minimally reactive epitope was expressed with a GST-tag and subjected to western blot. The results showed that a 10-aa peptide (145)RGDLQVLTPK(154) was the minimal unit with maximal binding activity to MAb 8E8. Subsequent alanine scanning mutagenesis studies revealed that D-147, Q(149) and V-150 are crucial for MAb 8E8 binding. Furthermore, the epitope was found to be highly conserved among different topotypes of serotype O FMDV through sequence alignment analysis and detection of MAb 8E8 for affinity to some isolates collected in China. Thus, the 8E8 epitope identified here should be helpful for designing epitope-based, intra-typic, cross-protective vaccines of serotype O FMDV. (c) 2010 Elsevier B.V. All rights reserved.